с использованием itertools.zip_longest
test_list = [
[('c1t1'), ('c1t2'), ('c1t3'), ('c1t4'), ('c1t5')],
[('c2t1'), ('c2t2'), ('c2t3')],
[('c3t1'), ('c3t2')],
[('c4t1'), ('c4t2')],
[('c5t1')]
]
from itertools import zip_longest
new_list = [(item,) for my_list in zip_longest(*test_list) for item in my_list if item]
print(new_list)
вывод
[('c1t1',), ('c2t1',), ('c3t1',), ('c4t1',), ('c5t1',), ('c1t2',), ('c2t2',), ('
c3t2',), ('c4t2',), ('c1t3',), ('c2t3',), ('c1t4',), ('c1t5',)]
или
new_list = [item for my_list in zip_longest(*test_list) for item in my_list if item]
, если желаемый результат равен
['c1t1', 'c2t1', 'c3t1', 'c4t1', 'c5t1', 'c1t2', 'c2t2', 'c3t2', 'c4t2', 'c1t3', 'c2t3', 'c1t4', 'c1t5']